The present invention refers to a method and to a station for unblanked sheet delivery in a machine which processes plate elements, comprising a delivery frame provided with jogging stops and transverse gripper bars. The respective ends of the gripper bars are fixedly attached to two respective flexible drive elements, preferably in the shape of endless loops, for conveying the sheets in process.
When diecutting cardboard sheets or plates in a diecutting press, it is possible, according to the kind of job carried out in the press, to collect the blanks separately in the form of distinct piles or to deliver the unblanked sheet, particularly if it is to be processed in another machine, after the sheet diecutting operation and before the blanking operation.
In the first case, the front edges of the respective sheets remain seized in the grippers of the gripper bar of the sheet conveying device and after the blanking operation, the waste of the sheet is driven by the gripper bar towards the waste removal station.
In the second case, the sheet is released by the gripper bar and a stripper pushes it backwards by coming against its front edge in order to take it out of the grippers and stack it on a single storage pile formed between vertical jogging stops adjusted to the size of the sheets to be stacked.
The use of a conventional stripper is necessary to stop the sheet in order to take it out of the grippers of the gripper bar. However, the stripper has to be moved in the opposite direction to the sheet in order to encounter the sheet by passing between the grippers of the gripper bar at the time when these grippers open. That is the reason for the back motion imparted to the sheet when stopping it. Considering the kinetic energy of the sheet at the time it encounters the stripper, its abrupt stopping with back motion causes deformation of the sheet which propagates like a wave through it. This deformation wave has a risk of breaking the nicks connecting the previously diecut blanks to the sheet or even connecting them together. This is obviously undesirable since these nicks should keep the sheet entire, despite the diecutting of the blanks, until the time chosen for separating the blanks.